Excavation mainly completed, ONKALO will now see building technology and structural work

In February, excavation of the ONKALO access tunnel reached 455 metres, which is the deepest location as per the existing plans. This does not mean that the work in the underground research facility would end. However, there will be a change in the construction work as the main emphasis will shift from excavation to building and structural work.

Posiva's Construction Manager Lauri Piitari, what are the next steps of building technology in ONKALO?
”We've installed the necessary building systems in ONKALO up to the chainage of 3,820 metres, from where they will continue to the chainage of 4,986 metres at the end of the access tunnel. Regarding building technology, HVAC and electrical work will be carried out in the underground research facility."

What structural work will be performed in ONKALO?
”Most of the structural work will be carried out on the technical level (-437 m). This comprises the rescue chambers concrete structures and concrete work in the lower end of the personnel shaft and the inlet air shaft.

Building Development Manager Lauri Piitari

In addition, about 60 metres of the access tunnel floor will be coated. The test version of the concrete floor tells indicates very extensively how the access tunnel floor should be coated. One parking hall has already been excavated on the technical level. Another garage will also be excavated on the same level, but this will take place next year after all the building systems have been installed."

Does this mean that there will be more excavation work done on ONKALO?
"More than 90% of the full scope of ONKALO has been excavated. When necessary, the excavation can continue according to the needs of the researchers, for example. We'll be finished with this year's excavation work by April, when we complete the latter demonstration tunnel and two shaft ends at a depth of 455 metres."

What kind of rescue chambers will there be on the technical level?
"The first part of rescue chambers, about 250 square metres in floor area, will house offices and social facilities. The facilities will act as a point of assembly deep in ONKALO in case something unexpected happens in the tunnel. Prior to the start of final disposal, the safety centre facilities will be equipped as required."

What will the walls of the access tunnel finally look like?
"The walls and roof of the tunnel have been sprayed with concrete as the excavation has progressed, and the spraying will extend all the way down.

This also concerns safety: nothing is to fall off from the walls and roof to the tunnel. The floor coating will be decided on after the test floor has been completed."

What else will take place at ONKALO site this year?
"Our goal is to raise-bore ONKALO's personnel and inlet air shafts from the depth of 455 metres upwards to the depth of 290 metres during the summer and autumn. The raise-boring of the exhaust air shaft is already complete.
Most of the underground work is synchronised with the construction work above ground. The reason for this is that the second stage of the hoist building will be launched at the end of the summer with excavation. The upper end of the personnel shaft will be located in this building."

View from the techical level

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